Optical gauge



June 6 1950 c. E. PoER OPTICAL GAUGE Filed Feb. 15, 1.946

INVEN TOR.

ArroRA/En CHAQL 5 E. ,DOE/z?,

AL /l J Patented `une 6, 1.950

PMENT SoWi-'GE .oPmIcAL GAUGE Calif.

i Apnlicaton February 15, 1946,-Seria1aN0.=-647,844

lf'his invention relates1 generally;y tolgaugesand measuring `instrnme'nts,...artid more. particularly to such instruments ada-ntediiorn'se. in machine `@Shop :practice-for the purposeof centering,. laying 911t,.-.or .locating:work pieces. Withreference .to

rotational, axes. Deyicesembodyinglthe present .inyentionglhave many., uses .Y outside' tlie"eld of machine siiop@prac-tice,ir andf the. particular. ap- -plica'tionslhereinafter. instancedarektherefore to be regarded merely as typical and not asi/nplying .any,.lilm-i tationon theJ eld .of use, of,.the.inven :171011.

s'ud January l' '2g 19.45,'.120 Donald Lacy Benton. Of

dps.; Angelesg California. Land.; isginf the L fnat. u`re. lof ,a improvement lonffthe.. device described "and Claimed '.thezein.

'Ilheffacurate .location off work fpiec'zes l in ma- ...012;4 grinding. operations ythereon normally. consti- `tutes-two separatessteps. v Fil-"st it. isgnecsary to accuratelyaestablish fther axis. ofoperational l'.rotation,that is 'then axis voi rotationb a ...drilL 'lboring' bar.. onlcntter .held .in'aldiill ingress',4 .boring millfrorfmllingl. machine; lprfthe a'X'isof .rotation .of..the ,Work held. .in'lathesgborin .'mi1ls,..and .the like. The. secon'dstep in accuratelylocating'the work 1:5iecemco'ncerns; itSelfWiththe .relativeloca- .cordnglLQi-t is,v necessary .tof provide.. Work.r locating .means capable ,'.of .l acurately.,fdeternining j the .positionfof wormpiecs Ito: a degree., foi.. accuracy .wn .Withinlsuchitlerancea Itljs a.prmary.qbiet. of; myfinvlentiontoypro- 'ideya Work locatingfinstument.. adapted to, .be heldmcluoks or .iotnergtollihbngl members HSk s'tr'umnt v,is held. l

. it is another .ob'j'ect ofmy `invention 'tol provide ,an optical Viewing 'system Vfor`ob`serving"ntlfiei 'pofsition ofthe. aforesaid indexfrelativefto reference marks placed on the' work piecelinvolvedwhich optical system; is.. adaptedljtoj substantially avoid Vprovidefan instrumentA as' described .which 'may be observed. 'from l .two ffda'metrically @opposed points of .viev/,Q thus.n1aking.'-pos'sible 'use' o1 the .halflgerrorleorrectn system; .'s'u'chlas is .frequentlyeyu'sed in; the.. precise. adjustment of 'srveying and. other instruments.

1 'It isf a..fi'n'"th'er.V object. Aof myinyention to. .pro-

vide.. an ir'istiiumentlas .described `l'ylh'ich f includes Q vzuneans f for.' .concentrating light.. on. the, 1 index .and reference. lines;` funder observation.

Itis a stillfurther object omy. imfe'ntionv to V.provide such an' instrument which'. .is simple, "rugged, easy gto. manufactureand use, and well adapted tov Withstandthe rou'gh usage'-often en- '.cointered 1in. machine shops.

"The foregoing.. and other. "objectsjA and 'advantages;offmyniention vx'vill'-,aplinear fr'om; the I ollowing description and attached .'.diawings }Briey. .ldesc1ibed,.- the devicelembodyng my .inlyentionaemnloys an; optical .reticle f hai/.ing .en- Qgravd theizeonas. an index,A alrne. line or' fcr'oss hair. Theinstrnmentlis .-provide'd'wth a .cylinvdrical sha-nklthusf adapting it. ,to be held inla Conventional 'Ja'yccabs .chuck,. or other .toolholding device ...Meana arey ,'.proyidedwithim thedn'stru'- 'nient .to Swing. .the-.indexinto .alignment with ,the rotational. axis ,ofthe .machine tool. which fthe instrment .is..held. Thelreticleis lobserize'd throngh. an .optical system Whichincliides af magnifying. lens. and;y a reflecting. ,p'ri'slrrn` the. purpose of these elements. .being .to .magriifygl'llie.A innige;l of ...the .ross .hairand to. lor'nglftheA lineof 'sight ...substantially...parallel .to `^the. above mentioned axia rotation, `thus.. ayoiding.l parallax.

embodiment ,of..my.inv.ention,reference shon'ld now .be Yhad. to fthe..attachedldrawings; .in which:

1 is anelevational.View.oifthefwdrkilocat- .inglinstrnnient[clamped in-a conilfntionalgma- 'chine' tool;

Fig. 2 is @elevation-a1. paftany sectioned-view "of Athe instrument'l taken along thelnefT-Z iin view of the device taken along the line 3 3 in Fig. 2;

Fig. 4 is a view of the reticle employed in my device as viewed through the optical system thereof; and

Figs. 5 through 8 inclusive, are diagrammatic representations of the field of View of the device illustrating various steps of a work locating operation.

Referring now to Fig. l, the numeral II) indicates generally an instrument constructed according to my invention. A cylindrical tube |I forms the main body of the instrument, and has slidably mounted at its lower end a draw-tube I2 carrying the optical system; and tiltably mounted in its upper end a cylindrical Shank I3 adapted to be held in a tool holding clamp of conventional design, as for example, the Jacobs chuck I6, shown in Fig. 1. The optical system employed in the device is bilaterally symmetrical about the vertical axis of the instrument, and comprises a Wedge-shaped prism I5 and a pair of plano-convex lenses I6 and I1. The lenses IS and I1 employed in the instrument illustrated have a focal length on the order of 30 mm. which I have found to provide an optimum degree of magnification and light concentration.

As will be seen from an examination of Fig. 3, the cross section of the prism I5 is in the shape of an isosceles triangle, having a relatively acute apex angle. In the present embodiment the prism I5 is constructed of flint glass and has an included apex angle on the order of 30. The Vertical sides of the prism I5 are cylindrically formed, thus making the base circular, and adapting the prism to be received inside the draw tube I2. The lower edge of the draw tube I2 is rolled inwardly, forming an annular constriction against which the prism I5 rests. In order to prevent chipping of the prism I5 where it rests against the constriction in the draw tube I2, the lower edge is chamfered, as can be seen in Fig. 3.

The two lenses I6 and I1 are mounted with their plane surfaces resting against the inclined surfaces of the prism l5 and are held in this position by a downwardly thrusting plunger I8, which thrusts against the convex surfaces ol' the lenses I5 and I1 near their upper edges, as can be seen best in Figs. 2 and 3. It will be seen from an examination of Fig. 3 that the downward pressure of the plunger I8 occasioned by the thrust of a conical spring I9 pressed against the upper end thereof and anchored in the draw tube I2, urgesthe lenses I6 and I1 to slide downwardly along the inclined faces of the prism I5, and hence outwardly with respect to the vertical axis of the instrument. The outward thrust of the lenses I6 and I1 just described is made use of to hold them in place by forming them into a wedge-shape as can be seen in Fig. 2. By virtue of this wedge shape, the outward thrust of the lenses I6 and I1 forces them to seat securely against the vertical edges 20 of a pair of openings formed in the walls of the draw tube I2. The downward thrust of the plunger I8 also forces the prism I5 to seat itself securely against the annular constriction in the lower end of the draw tube I2. Thus it will be seen that the mounting provided assures intimate contact of the lenses I 6 and I1 with the prism I5, holds all the optical elements in proper relative position, and provides shock absorbing means to prevent damage of the optical elements, such as might be occasioned by striking the lower surface of the prism I5 on metal or other hard surfaces.

The index 2| of the instrument is in the form o1 an interrupted cross line engraved in the lower surface of the prismy I5. The appearance of the index line 2| as viewed either from the bottom of the instrument, or through the optical system, as will be later described, is seen best in Fig. 4. This position of the index line 2| on the base of the prism I5 is such as to lie perpendicular to the plane of the drawing in Fig. 2 and parallel thereto in Fig. 3.

As has been previously mentioned, it is desirable that means be provided within the instrument for moving the index line 2| to a position where it intersects the rotational axis of the machine tool in which the instrument is held. To this end, the supporting shank I3 is tiltably mounted in the body tube II by means of a pair of pivot balls 22. The pivot balls 22 rest in a pair of diametrically opposed sockets 23 formed in the cylindrical surface of the shank I3. The balls 22 also rest in an annular groove formed by the edges of a pair of rings 24 and 25a, which are pressed into the upper end of the body tube II. Thus it will be seen that the shank I3 is adapted to tilt laterally about an axis defined by the opposed sockets 23. As a means for adjusting the shank I3 to any position along the line of tilting motion just described, a knurled adjustment screw 26 is threadedly engaged with the lower end of the shank I3.

As can be seen in Fig. 2, the screw 26 thrusts against the inner wall of the body tube II and extends through a clearance hole in said wall to a position for convenient manual adjustment. Opposing the thrust of the screw 26 is a compression spring 21 which thrusts at one end against the lower end of the shank I3, and at the other end against the inner wall of the body tube II. Thus it will be seen that the shank I3 is relatively rigidly held in any position to which it is adjusted by means of the screw 26. When the shank I3 is rigidly held in a tool clamping device, as for example the Jacobs chuck I4, as shown in Fig. l, then adjustment of the screw 26 serves to swing the entire instrument laterally about the line defined by the opposed sockets 23 in the shank I3. Thus, by manipulation of the screw 26, the index line 2| can be brought to a point where it interjsects the axis of rotation of the chuck I4.

In the operation of my device, the index line 2! is observed through the optical system, the line of sight of such observation being indicated generally by the line 25 in Fig. l and Fig. 3. From an examination of the optical path shown in Fig. 3, it will be seen that this path 25 passes through the lens I6, is reflected from an inclined surface of the prism I5, and thence passes downwardly to the base of the prism, wherein is engraved the index line 2|. As is well known in the optical art, even nely polished glass surfaces reflect light internally when placed in faceto-face physical contact. This internal reflection occurs because of the presence of a minute layer of air between the surfaces which is unavoidable even when the surfaces approach optical atness. Thus, an internal reflection occurs in the prism I5 in spite of the presence of the lens I6 or I1 against the outside of the refiecting surface. Also, it should be noted, that an internal reflection will occur whenever the angle of a light ray is greater than the critical angle of emergence, regardless of the relative indices of refraction of the lens and prism. As is indicated in Fig. l, the instrument I0 is so mounted relative to the work piece 26a that the 55 e6 asumen-pf saidewerkeniec aus imm fQneff thea-meioladiieultms eeecufiteredeln 10W wthe@friese-otprient.= therese Ofqoptial-fnsttumeets fOr-,.tllalccatien :.,:asi aribackgreunditq dex 0i-WorkfPeGeSeSf infill. fat-i @1.1M- iiais gillen difcult Ori-:impasible@Orf-adequate@illuminate f. 5 the referencef-f1i-neseundr. Qbseryetienf. .It

be Seen-.trom fanzexaminetivm offertes-1. 1i endif 3 that the loi-lateral symnietryspf thegoptical sysrf tem provides adequateiillumimtionfet ialltimes, .gsincef light str ilingeither. f y Vereference-f- ;eaSSeS'-nto theprismiis Wtedrfmmthe 0P- ystem-isfmdicatednn Ilias moeite innert-ace. andidrectedsslownwardlv hefte be notedetliaty the the W0rk-1By wayvfexample a ray :ill-gemellati-Yfacuitateifthe accurata i Y ine trom; a;,lielflt.-Smlrek .Staand-1^ enterirlgathe :reference-1ines:;therewith. `.opticalsystemfisshoyynin.Eigi -1 -,irhe;irst step. ne.cessarsezin.fa,cszurateltyr:center-fv `this1rayathroughtheaetel illustrated in Fig. 3 Where it;A n

I it passes through the lens I1 in v'ller'.suc,essi?! steps. 0f fr..-and.reects -fromethe Opposedinnerifaceepessing athis, indexeadi-ustmentfzare '.fillustretedi-ibrf-Elgsf: downwardaxandf; Qutsthrolush ,th defend-7., respectively; andsareerfolrriedff:asL corrism l5. efoiiows. :While efobserving e the .perimposed I4The innere-fece 'reetion '.yimages ofitheiindexfzand referenceflmes as. heref applies tothe; optica1; axis .:inbefore,.,statediv-theeworketable#9 is. mowed-t0 is.'thelineofrsisht@heller/nin Eig? 1 genera appearance st 'fdescribedealso .ilIn, `gra: ',sbringgone ofcthe;.'referenceline 28 `intorexact the oprima; .axis has beeniexnded {3h/1mg@ be .a .alienmentfwith;the; index 121:, :asf-.is indicated-@H125 .renaming surfaceiingaccordane with: Wellzln wn rFig'.; 5-,. the:chucklAsbeingsmanuallyrotated if optcaLpr-inciples-thus illustrI ing-thagfhe p A- necessary. aIhe-,pchucki I andgtqthe instrument -.-,.pea1fanee0f thereeideasw We@ tuhrollghy he 0: heldV thereby are;nowerotated.throughs- 180 lens I6 is `the .sameasthatwhichwould bernh- .ziandfiihe lindeX-.Zl-:fssObSeIYdslhlllghftheqlens served from an-;imaginary stationzpoint :11, i..,e:, theylens opposite-to.than-through vvhich; K i .the pinitialigObSeIYB/tion; was mideltewill be the direction yfrom,whichAy he Qtil@ b readilyiseensandapprecie d nati-the lateral 1 ,lies substantia1ly, paralleler()th is 0 :usymmetrygpfg the optical system. aires. ossible strument;;l0,theerroreospagllaxfisv 116,12. ,Yfy

v:observation .of` thef..-i ndex-, ne'.2l through either smaIl. :..ofythe-iensesslem :iLz-hencefebviatinsfthe.neces- KA35 In order that the optical system Whenathefeinstrument l @through :18.0% iustlf y,

probable, the index line oti, nv/ ith the zaxisgof rotationither claasy observed, .4c enthrough; the f optical fsy stern,ji havel ftheff appearance shown in .hereinit/Will beseen f, threaddly engaged that thef-ndexfline -2l: is isplacedhorizontally 1 Ampleclearance isrip-rogided `from the reference .lnefz28 A ha1f=errorc0rrec e-nermittheaclamning screw Seite e tion is novvgappliedgiby the-manipulation.rofitherein;therdraw tube I2 tobelretraeted adjustmentserevrgzgs previously described, retube YI t l 1e screvv ducing by one-half the displacement of index gretainthe dran/tube line 2| and=..r`eferenceailinifZBti-ithe field of View ,-gfldditional -protetiormmay.K .n l w .ft-after Lillie-1.4correction-.beine.indicated,inY Eig. 7. ...-rormof adust eapfinoi shewn piaceinyei; he 4One correction operation, as j., ji1st described, is:`;e5o 1ovver endoithebody:tube, er heiretr`ati o of usually VsufdicientTto bring `the v inglex'line '2| into the dravvg, tube. alignmentv withetheaxis-"of--rotationuHaving ad- .An additionalfadvantageachieved justedrxthe position of thegjndex, table 29de again use of ,the draw 4tubecon strucisic) armored to;, bring.the .referenceiline 28 finto lignis thatthefinstrurnent.,` ai..ment:.with.the..index line A2l If the,- l1aliV error. 1,55l -chuckv, asir-1 d .ieat edinn e;correctionhas beenipropQllyiestlxnated;ithelIldeX the; desired distance abov .;line.2limvill-still. be. aligned-;zwith thefreference ;,adj u stm llt ofptheqpticalgs tem elet' line 28 aften asecond,rotationpithe instrument Work surface made by operationfoil-ythedraw I0 through '180.MIf the second `rotation of the -gftube Floiacilitategthisgtypeoijfdinejadiustment instrument again displacesfthe index line .1.2i .andsca a thin ple iesshim-.gnay be.; ernfployedwwhose -thefreference-line 28; lanother-lialf-errorJcorrecthickness-,is nequal to-tha minimum; ist nce..,of

tion is applied in the manner just described. thereticle rompthe Y.,vvoirleiigig surface wdgichsvvill Having accurately aligned the index line with permit rotation of the instrument Without the axis of rotation, and having moved the Work scratching the reticle surface. The shim is table to bring the vertical reference line 28 into 65 placed on the working surface under the reticle alignment with said axis, the instrument may and the draw tube lowered into contact therenow be rotated through 90, the index observed with, at which point the screw 33 is then tightthrough either of the lenses I6 or I1, and the ened and the shim removed.

work table moved to bring the horizontal refer- While the operation of centering a pair of ence line 29 into alignment with the index 2|. 70 :crossed reference lines has been used herein to It will be readily appreciated by those skilled illustrate one possible use of the instrument, it in the art of machine shop practice that the is Well adapted to `many other uses. For exinstrument is capable of easily and accurately ample, by the provision of plugs with suitable locating work pieces by the method just reference marks placed thereon, cylindrical holes described. 75 in Work pieces or drill jigs may be accurately aligned with the spindles of drills and other machine tools. Devices embodying my invention also iind wide use in such machine shop operations as inspection of machined parts, measurement of such parts, duplication of hole patterns,

the advantages hereinbeiore'V limit myself to the details of construction or de-` n sign herein shown, other than as defined in the appended claims.'

I claim:

1. An instrument for observing the position of a work piece relative to a rotary axis which includes an optical system comprising in combination: an op-tical prism of isosceles triangular cross section having a pair of substantially identical surfaces diametrically opposed and symmetrically disposed about said rotary axis at an acute angle to one another, having a third surface normally disposed to said rotary axis, and having an index formed in said third surface; and a pair of substantially identical planoconvex lenses, each disposed with its plane surface in substantial contact with one of said pair of prism surfaces, whereby said index may be selectively observed by reflection from an inner face of said prism along either of two lines of sight oblique to, and diametrically opposed about said rotary axis.

2. In an optical gauge, the combination of: a shank; an optical reticle having an index line formed therein; longitudinally disposed supporting means articulately mounted at its inner end to said shank and adapted to support said reticle adjacent an outer end of said supporting means in a plane substantially normal to the axis of said shank; adjusting means operatively associated with said shank and supporting means whereby to move said reticle transversely of said shank axis, and in a direction normal to said index line; and transparent means mounted in said support having a pair of surfaces therein disposed at an acute angle to each other, disposed at substantially equal angles to said axis, and adapted to reflect rays striking the same at greater than a critical angle thereto and to transmit rays striking the same at less than said critical angle, said surfaces being disposed inwardly of said reticle whereby to reect an image of said reticle so that said image is visible along posed to saidv oblique line of sight whereby to magnify said reiiected image of the reticle.

4. The structure defined in claim 2 further characterized by having light condensing means mounted in said support and adapted to condense ambient light and direct the same through one of said surfaces against the other thereof whereby to reflect said light downwardly to illuminate the area closely adjacent said reticle.

5, In an optical gauge for adjusting work in a power tool to locate a given point in a relatively lixed member in relation to the axis of a rotatable member n said tool: a shank adapted to be secured to said rotatable member; a housing extending longitudinally from said shank, said housing having a pair of diametrically opposed lateral openings therein; bearing means connected between said shank and housing whereby to permit swinging motion of said housing about an axisadjacen't an inner end of said housing and transverse to said rotary axis; means to adjustably move said housing in Said swinging motion ;V and an optical prism having a base substantially normal to said rotary axis and a pair of inclined faces disposed at substantially equal angles to said base mutually intersecting at an acute apex angle along a line of intersection substantially transverse to said rotary axis, said prism being mounted in Said housing with said base adjacent the outer end thereof and with said inclined faces each underlying one of said openings, said base having an index line formed therein substantially parallel to said transverse axis whereby said adjustment serves to swing said index line laterally to intersect said rotary axis and whereby the image of said line reiiected internally from one of said inclined faces may be viewed through the other thereof and through one of said openings.

6. The construction set forth in claim 5 further characterized by having a pair of positive lenses, one mounted in each of said lateral openings whereby to magnify said reiiected image and whereby to concentrate ambient light entering said prism through said openings.

CHARLES E. POER.

REFERENCES CITED The followingreferences are of record in the iile of this patent:

UNITED STATES PATENTS 

